Stabilized lubricating grease compositions



Patented May 9, 1950 STABILIZED LUBBICATING GREASE COMPOSITIONS Herschel G. smiui, Wallingi'ord, and Troy L. cmtrell, Lansdowne, Pa., assignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application SerialNo. 94,25

Elia! 19, 1949,

9 Claims. (Cl. 252-424) This invention relates to stabilized lubricating grease compositions. and more particularly to grease compositions having increased stability against oil separation and structural breakdown at high and low temperatures, and improved resistance to oxidation.

This application is a continuation-in-part of our prior copending application Serial No. 44,577, filed August 16, 1948. In general, when greases are employed under operating conditions for extended periods of time, they have a tendency to become oxidized, resulting in the formation Of gummy substances which prevent satisfactory lubricating action. When this occurs, it necessitates complete change of the lubricating grease which has become fouled due to oxidative deterioration. Accordingly, it is highly desirable to increase the resistance of greases to such deterioration.

Another serious problem encountered in the use of grease compositions is that of bleeding." The tendency of a mineral lubricating oil base to separate or bleed from a grease composition in which the oil has been compounded is well known in the art. Excessive bleeding will'tend to result in a complete breakdown of the grease involved,

to the detriment of any mechanism lubricated thereby.

Still another serious problem is encountered when greases are employed at either relatively high or relatively low temperatures, which tend to promote structural breakdown of grease compositions.

Accordingly, it is an object of this invention to provide improved lubricating grease compositions characterized by their resistance to oxidation.

A further object of this invention is the provision of improved lubricating grease compositions having increased stability against oil separation and structural breakdown at relatively high and low temperatures.

These and other objects are accomplished by the present invention wherein we provide improved grease compositions comprising a mineral lubricating oil thickened to the consistency of a grease by a soap, and relatively small stabilizing amounts of a substantially neutral higher fatty mono-carboxylic acid ester of a fusible, soluble mono-alkylated phenol-formaldehyde condensation product, the higher fatty acid being selected from the class consisting of saturated and monooleilnic fatty acids having at least 8 carbon atoms, and the alkyl substituent Of the alkylated phenol having from 4 to 12 carbon atoms.

Such esters, which are added to grease compositions in accordance with our invention, aredescribed and claimed in our copending application hereinabove identified. As shown therein, the esters are prepared by esterification of a fusible, soluble mono alkylated phenol formaldehyde condensation product with ahigher fatty saturated or mono-olefinic mono-carboxylic acid containing at least 8 carbon atoms at a temperature not in excess of 500 F. The fatty acid is employed in substantially equlmolar amounts with the alkylated phenol used in making the alkylated phenol-formaldehyde condensation product, whereby the free hydroxyl groups of the alkylated phenol-formaldehyde condensation product are esterifled by the higher fatty acid to produce substantially neutral waxy esters. Conventional esterification catalysts, such as sulfuric acid and p-toluene sulfonic acid can be employed.

As stated, the alkyl substituent of the monoalkylated phenols employed in preparing the addition agents for use in accordance with our invention have from 4 to 12 carbon atoms. It is preferred to prepare these alkylated phenols by alkylation of phenol with an olefin having from 4 to 12 carbon atoms in thepresence of a concentrated sulfuric acid catalyst. Thus, representative olefins or olefin-containing materials which are employed for the alkylation of phenol are butene-l, isobutylene, the amylenes, refinery. gas, diisobutylene and triisobutylene. The use of diisobutylene is preferred since the alkylated phenol obtained is primarily para-(alpha, alpha, gamma, gamma) tetramethylbutyl phenol, which is particularly useful in preparing grease additives. However, the n-alkyl phenols having 4 to 12 carbon atoms in the alkyl substituent, prepared by alkylating phenol with an n-alkyl halide in the presence of a Friedel-Crafts catalyst such as aluminum chloride, can also be employed. Accordinglv, any mono-alkylated phenol having from 4 to 12 carbon atoms in the alkyl substituent is useful. Among these alkylated phenols are n-butyl phenol, sec-butyl phenol, tert-butyl phe- 3 nol, n-amyl phenol, sec-amyl phenol, tert-amyl phenol, n-hexyl phenol, n-octyl phenol, (alpha, alpha, gamma, gamma) tetramethylbutyl phenol, triisobutyl phenol, and mixtures thereof.

The use of alkylated phenols having an alkyl substituent of less than 4 carbon atoms is not satisfactory because (i) the resulting esterified condensation products prepared from such phenols are insumeiently soluble in mineral lubricating oils and mineral oil lubricant compositions to serve the functions of an efilcient additive and (2) it is difiicult to'seoure substantially neutral, oilsoluble products by simple esterification of the phenol-formaldehyde condensation product and the higher fatty acid. Similarly if the alkyl substituent of the alkylated phenol exceeds 12 carbon atoms, the resulting esterified condensation products tend to be unstable and to become insoluble in mineral oils. 7

The above described mono-alkylated phenols, before the esterification reaction, are first condensed in conventional manner with formaldehyde to produce a fusible, soluble alkylated phenol formaldehyde condensation product. The mol ratio of alkylated phenol to formaldehyde may'vary from 1:1 to 1:2. Either alkaline or acid condensing agents are employed, as will be understood in the art. The resulting condensation product is then dehydrated in the usual manner.

As stated above, suitable fatty mono-carboxylic acids which are esterifled with the phenolformaldehyde condensation product are the saturated and the mono-olefinic fatty acids having at least 8 carbon atoms. A preferred group of fatty acids are the fatty acids of from 8 32 carbon atoms. The saturated fatty acids include caprylic, pelargonic, capric, undecylic, lauric, myristic, palmitic', stearic, arachidic, behenic, carnaubic, cerotic, melissic and psyllaic acids. The mono-olefinic fatty acids include nonylenic, decylenic, undecylenic, oleic, ricinoleic, erucic and brassidic acids. Mixtures of fatty acids having at least 8 carbon atoms, as obtained from the saponification of fats and fatty oils for example, may also be employed. Naphthenic acids and Hydrofol acids (hydrogenated fish oil fatty acids) are also suitable saturated fatty acids.

When the fatty acid has less than 8 carbon atoms, the esterified condensation products tend to become hard and brittle and of poor solubility in mineral oils. These effects increase as the length of the fatty acid chain decreases. Accordingly, the fatty acid must have at least 8 carbon atoms.

The following example illustrates the prepara-- tion of the additives which may be employed in accordance with our invention.

. EXAMPLE I a. Preparation of alkylated phenol.Into a suitable reaction vessel equipped. with a stirrer and means for heating and cooling, there were charged 112 pounds (1 pound mol) of octylene (commercial diisobutylene) and 94 pounds (1 pound moi) of phenol. Agitation was be un and 10 pounds of 96 per cent sulfuric acid were gradually added. The temperature of the reaction was so controlled that it did not exceed 220 F. The resulting product was primarily para-(alpha, alpha, gamma, gamma) tetramethylbutyl phenol.

1). Preparation of alkylated phenol formaldefatty acids.

Male condensation product-To the alkylated phenol in the same reaction vessel and still containing the sulfuric acid, there were added pounds of a 37 per cent by weight aqueous formaldehyde solution. (2 pound mols of anhydrous formaldehyde). The mixture was agitated and heated at 160 R, and the temperature gradually increased to 220 1''. until all of the formaldehyde was consumed. The temperature was then raised to 300 1''. to dehydrate the condensation product.

c. Esteriflcation of alkylated phenol-formaldehude condensation product-To the dehydrated alkylated phenol formaldehyde condensation product, there were then added 284 pounds (1 pound mol) of stearic acid and the mixture was agitated and heated to 400 F. until esterificatlon was substantially complete as evidenced by the formation of no more water. The product was then permitted to cool. The product was a lightbrownish waxy material, resembling beeswax in odor and appearance. It had the following properties:

Specific gravity, solid state 1.11 Melting point: F., capillary tube 108-120 Neutralization No 8.6

We have found that the above described esters may be compounded with a wide variety of greases to impart advantageous properties thereto. Such greases may be described as mineral lubricating oils thickened to the consistency of a grease by suitable soaps. These greases themselves are well known in the art and may be manufactured by conventional methods. For "example, the mineral lubricating oil bases include paraflinic, naphthenic and mixed base mineral lubricating oils, representative examples of which are shown in the following table. As known in the art, the soaps used in thickening the mineral oil base to a grease are fatty acid soaps derived from fatty materials such as tallow, lard, cottonseed oil, stearic acid, soy bean fatty acids and various other fats and The metal of the soap can be an alkali metal, an alkaline earth metal, and various other metals such as lead, zinc, chromium, tin, aluminum, iron, cobalt, nickel, cadmium, mercury, etc. As will be understood by those skilled in the art, the soap and mineral oil base will be selected in accordance with the specific properties of the grease it is desired to manufacture.-

In accordance with our invention, small proportions of the herein-described esters in a grease will substantially stabilize the grease against bleeding and structural breakdown at high and low temperatures, and will improve the resistance of the grease to oxidation. The amount of ester used is sufficient to retard separation of oil from the grease or inhibit oxidation of the grease, the same amount of ester conferring both effects, and in general, small amounts, from 0.1 to 5 per cent by weight on the grease, will sufilce. The ester may be dispersed in an already formed grease by simple mixing, or it may be introduced during the manufacture of the grease, for example by dissolving it in the mineral lubricating oil base used in the manufacture of the grease.

As has been stated, the grease compositions of the present invention may be compounded from a. variety of lubricating oil base stocks. Table I, below, is illustrative of mineral lubricating oils which may advantageously be used as a base for the greases referred to it sets forth the inspection data of such oils.

1 BIOHM mm Peg wuo m m, mm on 011 g; on 011 mm, :51. no 21.0 3.4 21.4 a. iw' i- 000 m2 am 010 1,050 210 F..... 41.0 ass 150 50.0 01 Viscosi In 02 01 :0 Flash, of as as ass ass in Fire, 00. 406 410 an 440 m Pour, F l5 +5 10 +5 Color, NPA 10 us 1.1:; 4.75 3.0 4.15 Carbon RcsiduaPerCcnL- 000 0.08 0.01 1.10 000 or: Neutralization 0.-..---. an 0.00 0.00 0.05 0.06 0.00

The following example is illustrative of a preferred method of preparing a lubricating 0 m Ummmvod grease composition according to our invention.

itttr i tiflttm 00F) 0X88 EXAMPLE n a Bright Stock 150 UV/210' 5 Into a closed press r e steam heated kettle 833$ 3& 3L.'.%2i.i:fi: It equipped with double motion stirring paddles, gggg gi agigg ga 1 1) 0.1 0.1 were charged 15.65 parts by weight of Hydrofol acids substitgited ior 50 8811: and? 1.2 acids, 1.2 parts by weight of an ester prepared 232i? Dsmlmn in accordance with Example I except that Hydrogigfif m 262 fol acids were used instead of stearic acid, 2.05 Flow Poing" F parts by weight of hydrated lime in a slurry of ggr 5 ;g 4 parts water, and 17 parts by weight of mineral g 5 Sea: 170 m lubricating oils having the following charac- F Worked" 273 282 teristics and blended in the following proportions: gf gggg g fi o fi'figg 05 05 can AAR 14-01442 ssessa- Oxidation Test T:' fi' fi m 50 500 25 Mid-Continental bright $1906]! (150 SUV/210 Pressure Drop: Lbsw: 5 2) The kettle was closed, saturated steam applied to the heating jacket and the stirring mechanism started. After two hours an internal temperature of 290 F. and a pressure of 39 p. s. i. were attained. The supply of steam to the steam heating jacket was then cut off and the internal pressure of the kettle was reduced to atmospheric pressure by bleeding steam therefrom for a period of hour. Thereafter the kettle was opened to the atmosphere and the temperature of the contents was gradually raised to 240 F. over a V2 hour period and further gradually raised to 275 F. over another hour period while adding 13 parts by weight of the blended oil. Steam to the heating jacket'was again cut of! and 0.94 part by weight of stearic acid was introduced to the mixture. Following this, 51 parts by weight of the blended oil were added over a' period of 5 hour while cooling to 250 F., at which time 0.025 part by weight of water was added. The contents of the kettle were then cooled to 175 F. in the course of hour. Hydrated lime in the amount of 021 part by weight was then sprinkled slowly into the kettle over V4 hour period. Then 0.015 part by weight of water was added and the kettleclosed and stirred under 20 inches of vacuum for 2 hours while maintaining an internal temperature of 175 to 180 F. Grease was then drawn out of the kettle through a 60 mesh screen. The grease thus prepared had the following make-up and properties as compared to an otherwise identical grease not containing the ester.

Further grease compositions compounded in a i manner similar to that set forth in Example II and embodying the type of esters prepared as in Example I are illustrated by the following comparative examples:

EXAMPLE III ImGproved Unimproved rease Grease Make-u percent by Wt;

500 2.5 Texas Oil (500 SUV/F.) 74.4 75. 7 15(1) MC Bright Stock SUV/210 6. 5 6. 6 Calcium Soap of Hydrolol Acids-.- l3. 2 13:2 Sodium Soap of Hydrofol Aci 1. 8 l. 8 Calcium Soap oi Ole 2. 7 2. 7 Ester of Example I. l. 4

Inspection:

Dropping Point, F.-

ASTM B56642 227 Flow Point, F.

Navy Dept. S 14-G1d 258 Penetration, AS M D217-44T 77 F., 150 Sec:

Unworked 106 Worked 287 280 Free Acidity as Oleic Acid, percent l. 11 1. 0 Oil Separation, F., percent AAR M-9l4-42 0. 4 l6. 0 Freeling Point, F.

AAR M-9l4-42. --55 '--50 Mineral Oil Content, Bercent by Wt- 80. 9 3 Oxidation Test, 176 Hrs 500+ 60 Pressure Drop, Lbs 2 20 mm IV Im mvsd Unimpmved lab-u percent b Wt.:

Texas 05 (dill SUV/1m F.) 74.0 76.3 150 Mg Bright Stock (150 SUV/210' a 5 6 Calcium Soap oi BtcaricAcld. 14. a 14. Sodium Soap of Oleio Acid l. 1. Calcium Soap of Oleic Acid---.. 0. 0 0. Excess Alkal calculated as Ca(OH);. 0. (B 0. 0s Ester oi Example L 1.

Dro Point F. ASTM D566- 0??? -1 m 234 Pmstration, ASTM D217-44T- 77F.,l50G,5Sec.:

Unworked 210 21 .Worked 319 321 Free Acidity as Oleic Acid, percent-- 0. 55 0. 6 Mineral Oil Content percent by Wt 81. 4 82. 9 Oil Separation, 175 rcent AAR 11414-42 0. 2 l2. 0 Oxidation Test, 176 F., Hrs. 500+ 45 Pressure Drop, Lbs 2 a0 EXAMPLE V Imdmwed Unimproved rease Grease Make-u Per Cent by Wt.:

600 2.5 Texas Oil (500 SUV/100 F.) 74. 2 75. 3 150 MC Bright Stock (150 SUV/210 & 6 6 6 Calcium Soap of Hydrofol Acids 17. 0 l7. 0 Calcium Soap of Stearic Acid 0. 8 0.8 Excess Alkal calculated as Ca(OH): 0. 3 0. 3 Ester 0! Example I. l. 2 Inspection:

Dropping Point, F.

ASTM D566-42 22 282 Penetration, ASTM D2l7-i4T- 77 F., 5 Sec.:

Unworked 228 228 Worked 328 3% Free Acidity as Oleic Acid. Per Cent- 0. l5 0. 1 Oil Separation, 175 F., Per Cent- A R $14-42 nil 4. 0 Mineral Oil Content, Per Cent by 80.7 81. 9 Oxidation Test 176 F. Hrs 500+ 70 Pressure brop, Lbs 4 EXAMPLE V1 Irn roved Unimproved rease G Makeu Per Cent by Wt.:

500/2.5 TexasOil (500 SUV/100 F.) 73. 8 74. 9 15%1310 Bright stock (150 SUV/210 6 4 6 5 Calcium Soap of Hydroiol Acids.... 18.5 18. 5 Excess Alkali calculated as Ca(0H)1- 0. 1 0 l Ester of Example I l. 2 InspBction; P t F roppm om ASTiI B66642 246 244 Flow Point, F.

Navy Dept. S 14Gld 295 205 Penetration, ASI i D2l7-44 '1- 77 F., 150 G., 5 Sec.:

Unworked. 177 17'] Worked 254 253 Free Acidity as Oleic Acid, Per Cent- 0. 09 1. 0 Oil Separation, 175 F., Per Cent- AAR LII-Q1442 nil 7 0 Freezin Point, F

AA M-914-42 -50 Mineral Oil Content, Per Cent by Wt 80. 2 81.4 Oxidation Test, 176 F., Hrs 500+ Pressure D Lb so The remarkable stability of grease compositions containing the esters employed in our invention is readily apparent from the inspection data. shown in the foregoing examples. The oil separation test indicates that the grease compositions of our invention exhibit exceptional structural stability and reduced tendency toward bleeding. The oxidation test also indicates that the grease compositions of our invention exhibit an excellent stability against oxidation. The

oxidation test referred to hereinsbove is a modiilcation of the Norma-Hoflman tut method. Briefly, the test comprises weighing a total of 20 grams of the grease to be tested equally into five stainless steel sample trays, and placing the trays into a pressure bomb equipped with a valve and pressure gauge and adjusted to a volume of 173 cc.'i2 cc. The bomb is then closed and flushed five times by filling it with oxygen to about lb./sq. in pressure, and then allowing the oxygen to escape. The bomb is then filled with oxygen to lb./sq. in. pressure and immersed in an oil bath held at 176 F.:0.5 F. After two hours. oxygen is released from the bomb so as to adjust the pressure to exactly lbJsq. in. The pressure is read and recorded every two hours until the pressure drops 20 lb./sq. in., or for 500 hours if the pressure does not drop as much as 20 lb./sq. in. in that length of time. The oxidation stability of the grease is reported as the number of hours required for the pressure in the bomb to drop 20 lbs., unless this does not occur in 500 hours. In the latter event, the result is reported as 500+.

The grease compositions of our invention may include additional modifying agents, as will be apparent to those skilled in the art, provided they contain an ester as disclosed herein. Resort may be had to such modificatiom and variations as fall within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. A grease composition comprising a mineral lubricating oil thickened to a grease by a soap, and a small amount of a substantially neutral higher fatty mono-carboxylic acid ester of a fusible, soluble mono-alkylated phenol-formaldehyde condensation product, the higher fatty acid being selected from the class consisting of saturated and mono-olefinic fatty acids having at least 8 carbon atoms, and the alkyl substituent of the alkylated phenol having from 4 to 12 carbon atoms, said ester being present in an amount sufficient to retard oxidation of the grease.

2. The composition of claim 1, wherein the higher fatty acid is a saturated fatty acid.

3. The composition of claim 1, wherein the higher fatty acid is a mono-oleflnic fatty acid.

4. A grease composition comprising a mineral lubricating oil thickened to a grease by a soap,

and a small amount of a substantially neutral higher fatty mono-carboxylic acid ester of a fusible, soluble mono-alkylated phenol-formalde- Iii hyde condensation product, the higher fatty acid being selected from the class consisting of saturated and mono-olefinic fatty acids having from 8 to 32 carbon atoms, and the alkyl substituent of the alkylated phenol having from 4 to 12 carbon atoms, the molar ratio of alkylated phenol to formaldehyde in the alkylated phenol-formaldehyde condensation product varying from 1:1 to 1:2, said ester being present in an amount suflicient to retard oxidation of the grease.

5. The composition of claim 4, wherein the said ester is present in an amount of from 0.1 to 5 per cent by weight on the grease.

6. A grease composition comprising a mineral lubricating oil thickened to a grease by a soap, and a. small amount of a substantially neutral higher fatty mono-carboxylic acid ester of a fusible, soluble mono-alkylated phenol-formaldehyde condensation product, the higher fatty acid being selected from the class consisting of saturated and mono-oleilnic fatty acids having from 8 to 32 carbon atoms, and the alkylated phenol be- 9 ing (alpha, alpha, gamma, gamma) tetramethylbutyl phenol, said ester being present in an amount sufficient to retard oxidation of the grease.

7. A grease composition comprising a mineral lubricating oil thickened to a grease by a soap, and a small amount of a substantially neutral stearic acid ester of a fusible, soluble (alpha, alpha, gamma, gamma) tetramethylbutyl phenolformaldehyde condensation product, said ester being present in an amount suificient to retard oxidation of the grease.

8. The composition of claim 7, wherein the said ester is present in an amount of from 0.1 to 5 per cent by weight on the grease.

9. A grease composition comprising a mineral lubricating oil thickened to a grease by a soap,

- and a small amount of a substantially neutral REFERENCES CITED The following references are of record in the file of this patent: 1

UNITED STATES PATENTS Name Date Rochner et al Nov. 8, 1949 Number Certificate of Correction Patent No. 2,506,905 May 9, 1950 HERSOHEL G. SMITH ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 5, Table I, third column thereof, for 205 read 305;

and that the said Letters Patent should be read with this correction therein that the same may conform to -the record of the case in the Patent Office.

Signed and sealed this 25th day of July, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommz'ssioner of Patents. 

1. A GREASE COMPOSITION COMPRISING A MINERAL LUBRICATING OIL THICKENED TO A GREASE BY A SOAP, AND A SMALL AMOUNT OF A SUBSTANTIALLY NEUTRAL HIGHER FATTY MONO-CARBOXYLIC ACID ESTER OF A FUSIBLE, SOLUBLE MONO-ALKYLATED PHENOL-FORMALDEHYDE CONDENSATION PRODUCT, THE HIGHER FATTY ACID BEING SELECTED FROM THE CLASS CONSISTING OF SATURATED AND MONO-OLEFINIC FATTY ACIDS HAVING AT LEAST 8 CARBON ATOMS, AND THE ALKYL SUBSTITUENT OF THE ALKYLATED PHENOL HAVING FROM 4 TO 12 CARBON ATOMS, SAID ESTER BEING PRESENT IN AN AMOUNT SUFFICIENT TO RETARD OXIDATION OF THE GREASE. 